This invention relates to the field of spray painting apparatus such as spray guns and the like, and more specifically relates to spray guns of the type which are operated under high hydraulic fluid pressures and which utilize such pressures to assist in the atomization of the paint spray. Such paint spray apparatus may utilize hydraulic fluid pressures in the range of up to 2,000 pounds per square inch (psi). The highly pressurized paint fluid is forced through a very small paint spray orifice which is conventionally formed at the tip of a spray gun. Such spray orifices are typically of cross-sectional area of 0.0001 to 0.0007 square inches and are constructed from carbide steel in order to withstand the abrasive effects of high pressure, high velocity paint. The orifices are usually elliptical in shape and create a corresponding elliptical point spray pattern which is useful for obtaining the desired paint coverage on an article.
Since the spraying and atomizing of the paint is accomplished under high hydraulic fluid pressures, rather than under the influence of an auxiliary air source, this technique of painting is commonly referred to as "airless" spraying. One of the disadvantages inherent with apparatus which itilize the airless spraying technique is the potential for causing physical injury to a person coming in contact with the high velocity paint spray particles near the outlet of the spray orifice. When one examines the physical characteristics of a spray pattern emitted from an airless spray gun it is seen that the paint particles retain a partially-atomized fan-shaped characteristic for a distance of approximately 1/4 - 1 inch from the spray orifice, and thereafter they become fully atomized into fine droplets which are propagated forwardly to be deposited upon the article to be coated. Physical contact with the paint droplets after they have become atomized is generally harmless, for they have a reduced velocity which is insufficient for penetration of the skin. However, physical contact with the thin liquid paint sheet near the end of the spray orifice can have serious harmful effects, for the velocity of the paint particles in this region is high enough to penetrate the skin of a person, and can cause infection which may require medical treatment. It is therefore advantageous to provide some means for protecting the region near a paint spray orifice from coming into contact with any portion of a person's body. Of course, the form of protection selected to accomplish this purpose must also provide a paint spray operation without degradation or hindrance of the paint spray pattern.
In the prior art, various shielding mechanisms have been devised to project externally of the spray orifice and thus prevent human contact from a region near the orifice. However, these devices have suffered from the disadvantage that they often accumulate paint residue because of their proximity to the paint orifice, and further, they have sometimes interferred with the desired paint spray pattern being emitted from the spray gun. Other attempts at minimizing the harmful effects of inadvertent contact with the paint stream near the outlet of a paint orifice have dealt with providing various safety mechanisms to the spray gun trigger actuating apparatus. For example, co-pending U.S. patent application Ser. No. 450,927 owned by the same assignee as the present invention, provides one approach to disabling a spray gun actuating trigger whenever the spray tip orifice is being removed for cleaning or replacement. Various other trigger safety mechanisms have been utilized in the prior art to minimize the problem of inadvertent triggering of the spray gun.
The present invention provides an apparatus for fitting over the end of an existing spray gun and thereby preventing close physical contact by the operator or others to the region near the paint spray orifice. The invention further accomplishes this safety function without disturbing or interferring with the paint spray pattern being emitted from the spray gun. Further, the invention is adapted for convenient alignment with the elliptical spray orifice in a manner which always insures that the spray pattern is unencumbered. Further, the invention is removable with the spray tip when such removal becomes necessary for cleaning or other purposes, and is replaceable with the spray tip in a manner which retains the desired alignment with the elliptical spray orifice.